I’m a comics nerd, I think that’s pretty obvious by now, so jumping into one of the FOUR comics related shows this fall cause I already know who the characters are, what their backstories are, etc. But it’s not that easy for everyone and so DC Comics has released a free ebook with preview pages for several essential reads to get to know the characters and stories.
You’re not getting the full books, just some previews to give you a taste but it’s still really helpful if you aren’t familiar with the heroes and want to get the most out of each show (so far Gotham, Flash, and Arrow have been chock full of easter eggs for those in the know so it’s really worth while IMO).
The ebook is available from iTunes, Google Play, ComiXology, and Nook and Kindle.

@Raadhiyah not at all, if you want to read the comics it would be more like an expanded understanding of the little easter eggs and hints they give you in the show. as far as I know none of the shows are based on a specific story arc from comics, just general stories with some clues thrown in for anyone who's read the comics. what I will say is if you're a fan of the comics or Justice League watching Arrow be prepared for Ollie to be really different. I love it, but he is different.